Feeding wisteria

Trimming will undoubtedly help provided it's in a sunny position. You don't mention how long your plant has been there or how thick the main stem is, so I'll assume your plant has been in the ground up to five years.

You shouldn't need to feed, manure would be too rich. But it will appreciate a bark mulch and a 'tonic' such as sulphate of potash for the flowers. (Arthur Bowers do a range of tonics in plastic yellow boxes that have the advantage they don't suffer the wet - follow the instructions on the box).

And not for the first time I have recommend to people to check their soil pH. Yours should be between 6 & 7 for wisteria.

P.S. Ditto for your passion flower!

Thanks! I don't know how old it is but the main stem is a about 1.5 inches in diameter. My soil is neutral, I checked it when I moved in, but there are quite a lot of rhododendrons, hydrangeas, azaleas, roses and that ilk around about. (fairly heavy soil). I'll pop to my local nursery later for my sulphate of potash! Cheers!